Stack stabilizer for paper stacking machine

ABSTRACT

One or more wheels are rotatably supported by vertically swingable arms above the stacking station of a paper-stacking machine of the type wherein papers are stopped on a traveling conveyor belt by a limit stop, and succeeding papers are inserted into the bottom of the stack. When the stack is completed, the limit stop retracts, and the stack moves on with the conveyor belts. The wheels are initially held off the conveyor belts by an adjusting screw to allow the first few papers to be inserted into the stack without resistance, and then are picked up by the stack as it builds, pressing down lightly on the stack to hold it against falling or shifting. As the last few papers are being inserted into the bottom of the stack, the wheel arms pick up a spring load, causing the wheels to press down more firmly, holding the bottom papers against the conveyor belts with sufficient pressure to increase friction between the bottom paper and the belts, so that when the limit stop retracts, the stack will accelerate with the belts without pulling apart.

United States Patent Behrens et al.

[451 Apr. 23, 1974 STACK STABILIZER FOR PAPER STACKING MACHINE Inventors: Roy E. Behrens; Leo O. Donahue,

both of Highland, Calif.

Assignee: Graphic Engineers, Highland, Calif.

Filed: Mar. 29, 1973 Appl. No.: 346,042

References Cited UNITED STATES PATENTS 2/1972 Anastasio et al 214/6.5 X

6/1967 Donahue et a1 93/93 R 2/1953 Stencil 93/93 DP 6/1961 Monaghan 271/212 X Primary Examiner-Roy Lake Assistant Examiner.lames F. Coan Attorney, Agent, or Firm-Herbert E. Kidder [5 7] ABSTRACT One or more wheels are rotatably supported by vertically swingable arms above the stacking station of a paper-stacking machine of the type wherein papers are stopped on a traveling conveyor belt by a limit stop, and succeeding papers are inserted into the bottom of the stack. When the stack is completed, the limit stop retracts, and the stack moves on with the conveyor belts. The wheels are initially held off the conveyor belts by an adjusting screw to allow the first few papers to be inserted into the stack without resistance, and then are picked up by the stack as it builds, pressing down lightly on the stack to hold it against falling or shifting. As the last few papers are being inserted into the bottom of the stack, the wheel arms pick up a spring load, causing the wheels to press down more firmly, holding the bottom papers against the conveyor belts with sufficient pressure to increase friction between the bottom paper and the belts, so that when the limit stop retracts, the stack will accelerate with the belts without pulling apart.

7 Claims, 7 Drawing Figures msmmm w 15,805,971

SHEET 1 [IF 2 FIGi.

PATENTEU R 2 I974 SHEET 2 [IF 2 STACK STABILIZER FOR PAPER STACKING MACHINE BACKGROUND OF THE INVENTION The present invention pertains generally to paper stacking machines, and is an improvement on the counting and stacking apparatus shown and described in our US. Pat. No. 3,543,651. The apparatus of the patent is a machine for conveying papers and stacking them into stacks of predetermined count. A continuous line of overlapping papers travels along a belt conveyor to a stacking station, where the papers are stopped by a limit stop, causing the papers to accumulate into a stack as succeeding papers are inserted into the bottom of the stack. When a predetermined number of papers has been inserted into the stack, the limit stop retracted, momentarily retracted, allowing the stack to move on with the conveyor belts. As the trailing edge of the stack clears the retracted limit stop, the latter is raised to stop the next succeeding paper and thereby start a new stack.

While the apparatus of our patent has proven to be eminently satisfactory most of the time, there have been occasions when, as the limit stop retracts to release the stack, the conveyor belts would pull the bottom one or two papers part way out from under the stack. This is due to the fact that inertia holds the stack back while the conveyor belts are trying to accelerate the stack up to belt speed. Friction between the bottom paper and the conveyor belts is not enough to allow the bottom papers to accelerate the papers above. As a result, the bottom papers tend to pull out from beneath the stack. The problem is also aggravated by jets of air that are blown downwardly against the top surface of the papers that are being inserted into the bottom of the stack. These jets of air penetrate into the space between the bottom paper of the stack and the paper that is just being inserted, thereby forming a cushion of air which tends to lift the stack slightly. The air also acts as a lubricant between the adjacent surfaces of the papers, reducing friction between them and facilitating the insertion of papers into the bottom of the stack, particularly as the stack grows taller. However, the same air lubrication that facilitates insertion of the papers into the bottom of the stack also reduces the friction between the contacting surfaces of the bottom two or three papers, making it easier for the conveyor belts to pull the bottom one or two papers out from under the rest of the stack.

In the machine of our patent, there are wheels that rest lightly on the stack as it builds up, to stabilize the stack and hold the top papers from blowing away. It was found that if sufficient downward pressure was applied to the stacks by these wheels, the stacks would accelerate without having the bottom one or two papers pulled out by the conveyor belts. However, trouble was then experienced in building the stacks, as wheel pressure sufficient to prevent the bottom one or two papers from pulling out would create so much resistance that the papers could not be properly inserted into the bottom of the stack. Thus, it appeared that downward pressure applied against the top of the stack to prevent papers from pulling out at the bottom was not a satisfactory solution to the problem.

SUMMARY or THE INVENTION The primary object of the present invention is to provide a new and improved stack stabilizer, which holds the stack stable all during the time it is building up and which causes the finished stack to accelerate up to belt speed when the limit stop is retracted, without pulling out any of the bottom papers. This object is achieved by providing one or more wheels, which rest on the stack and rise with the latter as the stack builds up. The wheels are carried at the ends of vertically swingable arms, which are supported on other arms that are also vertically swingable, but are spring-loaded downwardly against rests. There is a lost-motion pivot connection between each of the wheel-supporting arms and the said other spring-loaded arm, which allows the wheel to rise freely with the stack until the last two or three papers are inserted into the bottom of the stack. At this point, the wheel-support arm picks up the springloaded other arm, and raises it from the rest against the pressure of the spring. The additional spring-loading on the wheel causes the latter to press down firmly against the top of the stack with enough additional pressure to increase the frictional resistance between the bottom papers and the conveyor belts, so that when the limit stop retracts, the stack accelerates up to belt speed without having any of the papers pulled out of the bottom thereof.

The foregoing and other objects and advantages of the invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment thereof, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary side elevational view of the stacking station portion of a counting and stacking machine, showing a stack stabilizer embodying the principles of the invention;

FIG. 2 is a top plan view of the same;

FIG. 3 is a view similar to FIG. 1, showing the stabilizer wheel riding up on top of the stack of papers, as the stack build up:

FIG. 4 shows the spring-loaded arm picked up by the wheel support arm as the stack is virtually completed, causing the wheel to exert a stronger downward pres sure on the stack so as to increase frictional resistance between the bottom papers;

FIG. 5 is an enlarged sectional view, taken at 55 in FIG. 3;

FIG. 6 is an enlarged sectional view, taken at 6-6 in FIG. 3; and

FIG. 7 is an enlarged sectional view, taken at 7-7 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, the reference numeral 10 designates in its entirety a stack stabilizer embodying the principles of the invention. Stabilizer 10 is mounted on the housing 12 of a counting and stacking machine of the type shown and described in our US. Pat. No. 3,543,651, to which reference may be had for details of its construction and mode of operation. Enclosed within the housing 12 is a drum (not shown) around which four laterally spaced conveyor belts 14 travel, carrying the stream of shingled papers with them. As

the papers come off the top of the drum, they leave the housing 12 through an exit 16, and move onto a stacking station 18 on the tabletop 20 of the machine. The papers are stopped and formed into a stack 24 by means of a retractable limit stop 22, which preferably comprises fingers projecting upwardly through slots in the tabletop 20 between the conveyor belts 14.

During normal stacking operation, the limit stop 22 is raised so that it stands in the path of the papers traveling on the conveyor belts 14. As each paper contacts the limit stop 22, it is stopped, and the next succeeding paper is pushed underneath the one above it, thereby building the stack from the bottom. When the stack reaches the predetermined number of papers, limit stop 22 is retracted below the surface of the tabletop 20, allowing the stack to move along the conveyor belts 14 to that portion of the tabletop beyond the limit stop. As the stack clears the limit stop, it is followed by a gap in the line of papers, and the limit stop fingers are raised through this gap so as to engage the leading edge of the next succeeding paper.

Insertion of the papers into the bottom of the stack is facilitated by air jets discharged from nozzles 26 that are mounted on the housing 12 at the exit 16. The airjets delivered by the nozzles 26 are directed downwardly against the top surface of the papers on the conveyor belts l4, and also in the direction of their travel, and the air jets impinge on the papers closely adjacent the stack. The streams of air penetrate into the space' between the bottom paper of the stack and the paper that is just being inserted, thereby forming a cushion of air which tends to lift the stack slightly so that the full weight of the stack does not press down on the paper being inserted. The air film also acts as a lubricant between the adjacent surfaces of the bottom paper in the stack and the paper being inserted, so as to reduce friction between them and thus facilitate the insertion of the papers into the stack.

The stack 24 is held down lightly by three laterally spaced wheels 28 that are located directly over three of the belts 16, as shown in FIG. 2. Each of the wheels 28 is journaled on the outer end of an arm 30, the other end of which is pivotally connected by pivot means 32 to a spring-loaded arm 34, which is supported on a transverse shaft 36 and is vertically swingable with respect thereto, the ends of shaft 36 being rotatably held by upstanding brackets 38.

Arms 34 are spring-loaded downwardly by coil torsion springs 40, one end 42 of which is hooked over the top of arm 34, while the other end 44 is attached to a collar 46, fixedly mounted on shaft 36. Springs pull the arms 34 downwardly against a rest 48, in the form of a transverse rod supported at its ends by upstanding brackets 50. I

Tension of the springs 40 is adjusted by turning the shaft 36, for which purpose a hex-head nut 52 is welded to one end of the shaft. To adjust tension in the springs, a wrench is applied to the nut 52 to turn the shaft, against the torsional resistance of the springs. Spring tension adjustment is held by a ratchet wheel 54 and pawl 56 (see FIG. 7), in which the wheel 54 is fixed to the shaft, and the pawl 56 is pivoted on the adjacent bracket 38.

Each of the arms 34 has a longitudinally extending, elongated slot 58 provided therein, through which the pivot 32 passes, as shown in FIG. 6. The pivot means 32 comprises a pivot bolt 60, which passes through a hole 62 in arm 30 near one end thereof. The bolt 60 has a shoulder that seats against the side of arm 34, and beyond the shoulder is a reduced-diameter portion 64 that passes through the slot 58,.and is threaded on its outer end to receive a washer 66 and nut 68. When the nut 68 is drawn up tight, the shoulder of the pivot bolt 60 is drawn against the side of arm 34, locking the pivot bolt solidly to the arm. However, by loosening the nut 68, the pivot bolt 60 can be shifted along slot 62 to move the stabilizing wheel 28 along the direction of travel of the papers, as shown in FIG. 3. Such fore-andaft adjustment allows the stabilizing wheels to be placed so that they spread their pressure over the paper at fore-and-aft spaced points as well as laterally spaced points. This is important, because the stack does not stay level as it builds up. The folded edge of the paper is thicker than the opposite edge, and as a result, the stack tends to build up higher at the folded edge. If the one side of the stack builds high enough, the top papers will become tilted, so that they tend to slide off. The wheels can also be adjusted so that the papers can be pressed down near their trailing edge, to keep them from sliding.

Mounted on the rear end of each of the arms 40 beyond the pivot means 32 is a lost-motion connection 70, comprising a vertically elongated loop 72 of strap steel that passes on both sides of the arm, as shown in FIG. 5. Screwed through tapped holes in the top and bottom of loop 72 are adjustment screws 74 and 76, the inner ends of which project into the interior of the loop and are engageable with the top and bottom surfaces of the arm 34. Lock nuts 78 hold the adjustment of screws 74, 76. The distance between the inner ends of screws 74, 76 is greater than the verticalwidth of the arm 34, and therefore the wheel support arm 30 is free to move through a substantial angular distance before the ends of the screws 74, 76 engage the arm 34. This allows the wheel 28 to ride up on the top of the stack 24, until the stack has built up almost to its full height, during which time the arm 30 swings freely about the pivot 32, without raising the arm 34. As the lost-motion connection is on the side of pivot 32 opposite the wheel 28, the loop 70 swings downwardly when the wheel 28 swings upwardly. When only the last two or three papers remain to be inserted into the bottom of the stack, the top adjustment screw 74 abuts against the top surface of arm 34, preventing any further downward movement of the loop 72 relative to the arm 34. This causes the arm 30 to pick up arm 34 and start raising it about the shaft 36. As the free end of the arm 34 lifts up from the rest 48, the spring load exerted by springs 40 is applied to arm 30, increasing the pressure of the wheels 28 downwardly on the top of the stack. This has the effect of increasing the frictional resistance between the bottom papers just as the limit stop 22 is about to be retracted. The increased frictional resistance between papers due to the additional downward pressure on the stack exerted by the spring-loaded wheels 28 causes the stack 24 to cohere as the stack is accelerated up to belt speed by the conveyor belts 14. As a result, there is no tendency for the conveyor belts to pull the bottom papers out of the stack.

As the trailing edge of stack 24 clears the retracted limit stop 22, there is a gap in the papers, through which the limit stop is raised back up to its normal operating position, where it engages and stops the next succeeding paper, to start a new stack. As the stack moves out from under the wheel 28, drops down to a position just a fraction of an inch above the tabletop, where it is held off the belts by engagement of the bottom screw 76 with the under side of arm 34. Thus, the lost-motion connection 70 and adjusting screw 75, 76 allow the wheels 28 to be adjusted both for the elevation of the wheels above the belts at the start of the stack-building operation, and the elevation of the wheel, at which the spring-loaded arm 34 is picked up by arm 30, which occurs just as the stack is virtually completed.

While we have shown and described in considerable detail what we believe to be the preferred form of our invention, it will be understood by those skilled in the art that the invention is not limited to such details, but may take various other forms within the scope of the following claims.

What we claim is:

1. For use with a stacking machine having conveyor belts that transport a continuous overlapping stream of papers to a stacking station where the papers engage and are stopped by a retractable limit stop, the succeeding papers being inserted into the stack at the bottom thereof, and said limit stop being retracted when the stack has been built up to full height, to allow the stack to be carried away by the conveyor belts, an improved stack stabilizer comprising:

a wheel resting on the top of said stack and movable vertically therewith as the stack builds up, said wheel extending a relatively light downward pressure on the top of the stack to stabilize the same; and

means for causing said wheel to exert a considerably increased downward pressure on the stack just as the last few papers are inserted into the stack and just before the limit stop is retracted, and suddenly increased downward pressure exerted on the stack by said wheel causing frictional resistance between the papers in the stack to be increased so that said stack coheres when the limit stop is retracted and the stack is suddenly accelerated to belt speed by the conveyor belts, without having any of the bottom papers pulled out of the stack.

2. The apparatus of claim 1, wherein said wheel is journaled on a support member that is movable vertically, and means is provided whereby said support member picks up a downwardly-directed spring load as said stack reaches a predetermined height.

3. The apparatus of claim 1, wherein said wheel is 5 journaled on one end of an arm, the other end of said arm being pivotally supported for vertical swinging movement of the arm; a spring-loaded member adjacent said arm; and a lost-motion connection between said arm and said member, whereby the arm picks up the spring-loaded member just as said stack reaches a predetermined height.

4. The apparatus of claim 3, wherein said springloaded member is a second arm closely adjacent said wheel-support arm, said second arm being pivotally supported at one end for vertical swinging movement and extending alongside and generally parallel to said wheel-support arm; spring-load means acting on said second arm to pull .the free end thereof downwardly against a rest with a strong spring pressure; and a lostmotion connection between said wheel-support arm and said spring-loaded arm, whereby the wheel-support arm picks up the spring-loaded arm as said stack reaches a predetermined height.

5. The apparatus of claim 4, wherein said wheelsupport arm is pivotally connected to said springloaded arm.

6. The apparatus of claim 5, wherein the pivotal connection between said wheel-support arm and said spring-loaded arm is adjustable along the length of the latter.

7. The apparatus of claim 5, wherein said lost-motion connection comprises a member fixed to said wheelsupport arm at a short distance from said pivotal connection and extends vertically to points above and below said spring-loaded arm; and adjustable stops on the top and bottom ends of said member engageable with the top and bottom sides, respectively, of said spring-loaded arm when said arms have moved through a predetermined angular distance, whereby said wheelsupport arm is free to rise with the top of said stack until the latter has reached a predetermined height, at which point said spring-loaded arm is picked up by the wheel-support arm.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 05 971 Dated April 23, 1974 Inventofl ROY E. BEHRENS and LEO o. DONAHUE It is certified that, error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

lines 18 and 19 should read:-- has been inserted into the stack, the limit stop is momentarily retracted,

allowing the stack to--.

Column 1,

Column 2, line 43, "build" should read --bui1ds--.

Signed and sealed this 10th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON, JR. I C. MARSHALL DANN- v Attesting Officer Commissioner of Patents USCOMM-DC 60376-P69 LLSI GOVERNMENT PRINTING OFFICE I!" O3-JJ| FORM PO-IOSO (IO-691 

1. For use With a stacking machine having conveyor belts that transport a continuous overlapping stream of papers to a stacking station where the papers engage and are stopped by a retractable limit stop, the succeeding papers being inserted into the stack at the bottom thereof, and said limit stop being retracted when the stack has been built up to full height, to allow the stack to be carried away by the conveyor belts, an improved stack stabilizer comprising: a wheel resting on the top of said stack and movable vertically therewith as the stack builds up, said wheel extending a relatively light downward pressure on the top of the stack to stabilize the same; and means for causing said wheel to exert a considerably increased downward pressure on the stack just as the last few papers are inserted into the stack and just before the limit stop is retracted, and suddenly increased downward pressure exerted on the stack by said wheel causing frictional resistance between the papers in the stack to be increased so that said stack coheres when the limit stop is retracted and the stack is suddenly accelerated to belt speed by the conveyor belts, without having any of the bottom papers pulled out of the stack.
 2. The apparatus of claim 1, wherein said wheel is journaled on a support member that is movable vertically, and means is provided whereby said support member picks up a downwardly-directed spring load as said stack reaches a predetermined height.
 3. The apparatus of claim 1, wherein said wheel is journaled on one end of an arm, the other end of said arm being pivotally supported for vertical swinging movement of the arm; a spring-loaded member adjacent said arm; and a lost-motion connection between said arm and said member, whereby the arm picks up the spring-loaded member just as said stack reaches a predetermined height.
 4. The apparatus of claim 3, wherein said spring-loaded member is a second arm closely adjacent said wheel-support arm, said second arm being pivotally supported at one end for vertical swinging movement and extending alongside and generally parallel to said wheel-support arm; spring-load means acting on said second arm to pull the free end thereof downwardly against a rest with a strong spring pressure; and a lost-motion connection between said wheel-support arm and said spring-loaded arm, whereby the wheel-support arm picks up the spring-loaded arm as said stack reaches a predetermined height.
 5. The apparatus of claim 4, wherein said wheel-support arm is pivotally connected to said spring-loaded arm.
 6. The apparatus of claim 5, wherein the pivotal connection between said wheel-support arm and said spring-loaded arm is adjustable along the length of the latter.
 7. The apparatus of claim 5, wherein said lost-motion connection comprises a member fixed to said wheel-support arm at a short distance from said pivotal connection and extends vertically to points above and below said spring-loaded arm; and adjustable stops on the top and bottom ends of said member engageable with the top and bottom sides, respectively, of said spring-loaded arm when said arms have moved through a predetermined angular distance, whereby said wheel-support arm is free to rise with the top of said stack until the latter has reached a predetermined height, at which point said spring-loaded arm is picked up by the wheel-support arm. 